1. Field of the Invention
This invention relates in general to subsea wellhead equipment, and in particular to a casing hanger seal member having a mechanism for locking the seal in place.
2. Description of the Prior Art
In a subsea well of the type concerned herein, a wellhead housing will be located on the sea floor. Casing will extend into the well and be supported at the wellhead housing by a casing hanger. A seal or packoff locates between the casing hanger and the wellhead housing to seal this annulus space.
The casing seal is normally set by compression. The compressive force required can be quite high. One way in which to achieve this high compressive force is by using a nut and thread. Another method utilizes a hydraulic actuated running tool.
While both of these types are satisfactory, there are occasions when the wellhead pressures are not expected to be very high. If the seal did not require a very high compressive force for setting, a simpler running tool could be used.
Also, there are occasions when it is desirable to use a seal that could be easily retrieved along with the casing hanger. This occurs particularly when drilling an exploratory well. If the well is abandoned, at least part of the casing may be salvaged. If not abandoned, the seal could be retrieved and replaced with a more permanent seal. Consequently, there is a need for a remotely energized seal for a casing hanger that does not require complex running tools and which is easily retrieved.